Patent GB-615030-A (GB)
Title: Improvements in or relating to operating means for gas-blast electric switches
IPC: H01H33/32
Filed: 1946-08-16
Abstract: 615,030. Air-break switches. ETABLISSEMENTS MERLIN & GERIN. Aug. 16, 1946, No. 24387. Convention date, Dec. 4, 1942. [Class 38 (v)] In a gas-blast circuit-breaker with one or more pneumatically-actuated contacts adapted to be opened against spring pressure, the gas blast is limited to the time necessary to extinguish the arc and the contacts are held open for a predetermined time after the extinction of the arc. On fault, a current transformer 42 energizes a relay 43 to open a valve 18 and so supply compressed gas from tank 15 to piping 50, 23, thus closing decompression valves 20, 31, 41, and releasing retarded orifices 30, 40, 48. A valve 17 is opened by gas from piping 54 to operate a blast valve 16 which passes gas to the break chamber 6, thereby opening tubular contacts 1, 2, by acting on a spring-urged piston 3. The gas discharge through contacts 1, 2, causes valves 13, 14 to open to atmosphere, thereby extinguishing the arc between contacts 1; 2, and so de-energizing the transformer 42 and relay 43. The valve 18 remains open, however, due to a holding contact 44 which remains closed until the rod of a piston 46 rises to open a series contact 45. Meanwhile, a valve 25 fed through the orifice 30, vents piping. 54 to atmosphere at 26, and at 27 shuts off the gas supply to valve 17, which, with valve 16, closes. The pressure in chamber 6 therefore drops and, at 52 per cent of the operating pressure, valves 13, 14 reclose, the pressure remaining on piston 3 preventing reclosure of contacts 1, 2. When the piston 46 moves up sufficiently, contact 45 is opened and the valve 18 closes, thereby venting the pipe 50 to atmosphere, the contact 45 remaining between its upper and lower co-operating contacts, since piston 46 is prevented from moving down by a one-way valve 49. Valves 31, 41 are thus opened to atmosphere before a valve 36 has time to open to supply gas to a piston 32 operating an isolating contact (not shown). The valve 20 is also opened to vent the chamber 6 and allow the contacts 1, 2 to reclose. If line conditions are normal again, the piston 46 has time to move down slowly due to leakages and the system returns to normal, but if contacts 1, 2, reclose on to a fault, the relay 43 is energized again and the valve 18 re-opens, the contacts 1, 2 being re-opened in the same way as before. This time, however, the piston 46 causes contact 45 to bridge upper contacts 45*. The eventual opening of-valve 25 to atmosphere by relay 43 is not therefore directly followed by reclosure of valve 18, and so valve 36 has time to cause opening of the isolator which, at the end of its stroke, opens a contact 51 to cause valve 18 to close. The isolator can be reclosed when desired by supplying gas to a pipe 34. In Fig. 2 (not shown), the valve 21 is closed by gas from valve 17, the gas in pipe 23 operating a further decompressing valve to control the venting of valve 21. In Fig. 3, the pressure on the piston 3 is arranged to be independent of that in the chamber 6. A spring- opposed piston 61, operated by the gas in the pipe 23, rotates a cam 59 through shafting 60 and a rack-and-pinion, so as to allow a valve 57 to close. When the pressure builds up in a conduit 8 the valve 57 opens and the gas flows through a tube 58 to the piston 3. When the valve 16 recloses and the pressure in parts 6, 8 drops, the valve 57 recloses and maintains the pressure on piston 3, until valve 18 recloses and, pipe 23 being vented, the piston 61 returns to normal, causing the cam 59 to open the valve 57 and allow the contacts to reclose. The pressure on the piston 3 may also be rendered independent of that in the conduit 8 by using an inlet valve, supplying gas to the piston 3, and a separate cam-operated outlet valve venting to atmosphere, Fig. 4 (not shown). In a modification of Fig. 3, the piston 61 may be actuated by gas from the valve 16, under control of the pressure in pipe 23, Fig. 5 (not shown). In a further modification, Fig. 6, the gas to the piston 3 passes through a valve 69 and an insulating tube 68, a venting valve 70- being closed by the gas in the pipe 23. When the valve 18 is reclosed, valve 70 opens and allows the contacts 1, 2 to reclose. The parts 60, 68 may be inside or outside the conduit 8, and the tubes 58 may be of insulation, or of semiconducting material, or insulation covered with a semi-conducting layer so as to form shunt resistances. The contacts 1, 2 may be tubular, as shown, or one or both may be solid. Specification 522,514 is referred to.